

nodulose al at lower end, transparent, are usuall) simpje, but emit 



on .ill sides .it shorl intervals throughout their whole length numerous lateral root-hairs, long 

 and transparent, which, branching dichotomously, rapidly taper into very fine fibrils 



\ ii|> into the stipes, the transition into the typical stipes-filamenl 



it-hairs gradually become stouter, thicker and interwoven, and so are 



il "crampons 01 abbreviated dichotomous lateral branchlets, the calcified 



with those of adjacent branchlets to form the cortical layer of the 



I i ;i lateral branchlets have the appearance of standing on a pyramidal 



th( constriction found near 1 1 h ■ base ol all branches except the rooi fibrils. 



min filaments ot the stipes ma) 1"- straight or flexuose, cylindric or nodulose, 



simpl .paringly dichotomous. At the apex of the stipes thej lose their lateral branchlets, 



.kcd with granular contents, increase in size and acquire a thicker wall; then 



jing from the stipes they branch repeatedly and dichotomously, become more or less 



calcified and constitute the free filaments of the capitulum. These free filaments as seen in 



herbarium specimens present the appearance of an inner green tube which has shrunk away 



from the rigid outer calcified sheath. (This is sometimes less obvious in /'. dumetosus, in 



which species the filaments are but slightly calcified I 'he outer calcified sheath has the 



appearance of being perforated (compare fig. 182) by numerous small rounded pon-s sec p. 102 . 



Il" examined in a dry state muler the microscope these are seen to consist of minute spherical 



bubble-like chambers as describetl by Montauxi (loc. cit.) for his P. arbuscula each opening 



b) a minute ostiole in the delicate calcified pellicle that covers them (compare also the further 



remarks on pp. o and 102). 



According to Woronini the calcium carbonate does not begin to form upon the filaments 

 ot /'. mediterraneus until the end ut the summer, so that the young ends of the filaments 

 stand out green anti soft from the hardened calcified thallus of the previous years. 



The filaments "f Penicillus are constricted at intervals, which may be long or short 

 according to the species. The walls at these points become much thickened and often transversely 

 striate on the outside, while communication along the filaments is maintained through a much 

 narrowed opening. Stoppers have been described and figured by Woronine for /'. mediter- 

 ranen*, similar to those found in Codium (see p. 5). 



Development. There are two distinct forms of development in this genus according 



t<> whether the formation of the stipes follows or precedes that of the comal filaments. In two 



of the species, /'. nodulosus and P. mediterraneus, the free filaments which form the primitive 



capitulum are developed in the young plant immediately above the rhizoids, without any inter- 



tte stipes. the stipe-, being gradually huilt up later. This is mentioned 1>\ Harvey for P. 



arbuscula 1= /'. nodulosus) Phyc. Austr. vol. I. tab. XXII. and by Woronine for /'. mediter- 



Ann. Sci. Nat. 4 1 ' sér. XVI. [862. pp. 208 i\\). In Kew Herbarium there are 



ens of /'. nodulosus in which the primary ascending filaments or primitive capitulum 



fully beaded and gradually produce "crampons" or lateral branchlets. These crampons 



to form a cortex which envelopes and binds together the primary filaments into a 



md stip' 



